Provide access to a write only value of type w.

Run the Writer effect and return the final value along with the final output (via Effectful.Writer.Static.Local).

Run a Writer effect and return the final output, discarding the final value (via Effectful.Writer.Static.Local).

Run the Writer effect and return the final value along with the final output (via Effectful.Writer.Static.Shared).

Run the Writer effect and return the final output, discarding the final value (via Effectful.Writer.Static.Shared).

Append the given output to the overall output of the Writer.

Execute an action and append its output to the overall output of the Writer.

Execute an action and append its output to the overall output of the Writer, then return the final value along with a function of the recorded output.

listens f m ≡ second f <$> listen m

Assign a label to an effect.

Note: labeled effects are best used together with the effectful-plugin package, as it significantly improves their usability.

The constructor is for sending labeled operations of a dynamically dispatched effect to the handler:

>>> import Effectful.Dispatch.Dynamic

>>> :{
  data X :: Effect where
    X :: X m Int
  type instance DispatchOf X = Dynamic
:}

>>> :{
  runPureEff . runLabeled @"x" (interpret_ $ \X -> pure 333) $ do
    send $ Labeled @"x" X
:}
333